Welded structure



Feb. 11, 1958 w. 1-1. PETERSON WELDED STRUCTURE 3 Sheets-Sheet 1 FiledDec. 9, 1954 I nven for illiamliPferJon Feb. 11, 1958 P w. H. PETERSON,897

WELDED STRUCTURE Filed Dec. 9, 1954 3 Sheets-Sheep 2 will I fnveniorWilliam HPeierson .Aiiorney Feb. 11, 1958 w. H. PEQTERSON 9 WELDEDSTRUCTURE Filed Dec. 9, 1954 s Sheets-Sheet a .lnv enfor Willi amH Pei''l'SOn United States Patent ice WELDED STRUCTURE William H. Peterson,Homewood, Ill., assignor to Pullman-Standard Car Manufacturing Company,Chicago, 11]., a corporation of Delaware Application December 9, 1954,Serial No. 474,109

18 Claims. (Cl. 189-36) This invention relates to the prevention ofearly brittle fracture in welded structures, particularly in mild steelwelded structures.

While the phenomenon of brittle fracture of steel has been recognizedalmost since the introduction of Bessemer steel in 1875, and somestudies were made at different times in various countries, very littlewas known regarding it. Largely as the result of numerous structuralfailures due to brittle fracture, in welded merchant ships early inWorld War II, extensive studies have been made during the past fifteenyears which have shed somewhat more light on the problem, largely in thedescription of phenomena associated with this type of fracture. It mayfairly be said, however, that so far such studies have revealed mainlythe extreme difficulty not only of solving the problem of brittlefracture but of even determining the basic causes thereof and theconcepts involved.

Brittle fracture is not limited to welded structures, and as it relatesto welded steel structures is not confined to ships, presenting problemsin practically all types of such structures, and particularly though notnecessarily those subjected to relatively low temperatures. Only a fewof the practically innumerable welded structures subject to brittlefracture and to which the present invention is applicable to preventsuch failure are specifically disclosed herein. As one example, freightcar underframes have unavoidable points of stress concentration at whichbrittle fracture sometimes occurs under cold weather conditions, onesuch point, for instance, being found in the body bolster. The bodybolster is formed with at least one vertical web or diaphragm welded tohorizontal top and bottom cover plates and terminating closely adjacentto the center sill, in many cases contacting and being welded to thecenter sill. At the inner corners defined by the web and cover plates,points of high stress concentration exist, due to residual stressesresulting from shrinkage of the welds connecting the web and plates, orto triaxial combinations of tensile stresses resulting from appliedload, or to the vector sum of both types of stresses.

Thus, a particular combination and magnitude of stresses exist at eachsuch point in a welded structure, as in the bolster, which will causeextensive fracture of the structure at loads frequently experienced inservice at low temperatures. The occurrence of brittle fracture in. mildsteel welded structures is characterized by virtually no flow of thematerial, and little energy is required to, propagate extensivefractures as compared to ductile fracture. Generally, highly localyields with beneficial redistribution of stresses can be effected byplastic flow of the steel due to its normal properties, leaving thestructure perfectly useful. In cases where low temperature so changesthe properties of the material as to prevent such plastic deformation,brittle fracture is very apt to occur when the yield point is reached.Obviously, the structure retains its serviceability after undergoingsmall local deformations, whereas if it is fractured its serviceabilityis lost, as in the case of the railway car bolster,

2,822,897 atented Feb. 11, 1953 for example. It has been found that bythe introduction of a rounded hole closely adjacent the point of stressconcentration, considerable plastic flow can desirably be attained inthe structure at such location, so as to prevent brittle fracture at lowtemperatures, without appreciably affecting the structure adverselyunder normal conditions, it being the aim to provide plasticity in astructure where otherwise plastic yielding of the material could notoccur, thereby increasing in great degree the work required to causefailure of the structure. This is of great importance in resistingdynamic loads. Such an opening at the same time directs applied stressesaway from the point of concentration.

It is therefore a principal object of the invention to provide forplastic flow in welded steel structures at locations where brittlefracture might otherwise occur due to lack of plasticity.

Another object is the provision in welded steel structures of means foreliminating the effect of high stress concentrations in causing brittlefracture, by providing plasticity at points of such concentrations.

Another object is the provision of means for preventing brittle fractureof welded steel structures due to high stress concentrations.

It is also an important object of the invention to provide in weldedsteel structures, wherever a weld connection of one plate-like member toanother terminates in a region of high tensile stress, means in suchregion to prevent brittle fracture beginning at the region.

Another object is the provision, in welded steel structures havingmembers connected together by a weld terminating at a region of hightensile stress, of means in such region directing tensile stresses awayfrom the weld termination and providing plasticity in the region toprevent brittle fracture. 7

Still another object is the provision of a method of preventing brittlefracture in welded steel structures by providing for plasticity in suchstructures.

Other and further objects, advantages, and features of the inventionwill be apparent from the following description and the accompanyingdrawings, in which:

Fig. 1 is a perspective view of a railway freight car underframeconstruction embodying the present invention;

Fig. 2 is an enlarged perspective view of a portion of the underframeshown in Fig. 1, in inverted position, and showing a rounded opening ina horizontal cover plate closely adjacent a weld termination of avertical web plate;

Fig. 3 is a perspective view of a structure of horizontal and verticalplates Welded together, comparable to the cover plate and web plateconstruction shown in Fig. 2, and showing the region of brittle fracturedue to applied tensile stress and lack of elongation of the structure;

Fig. 4 is a perspective view of a structure similar to that of Fig. 3but provided with a circular opening in the horizontal plate in linewith the vertical plate closely adjacent the toe of the weld connectingthe plates;

Fig. 5 is a view of the structure of Fig. 4 after application of tensilestress thereto, showing the plastic deformation thereof withoutfracture;

Fig. 6 is a fragmentary perspective view of aship deck, partly insection, including a welded hatch corner and a clevis, showing theapplication of the invention tothis type of structure;

Fig. 7 is a perspective view'of an I-beam with a clevis welded to itslower flange, showing the application of the invention to such astructure;

Fig. 8 is a perspective view of cylindrical'pressure tank to which asupport is welded, showing the application of 3 view taken along theline 9--9 of Fig. 8, showing in greater detail the application of theinvention.

Referring first to Figs. 1 and 2 of the drawings, there is shown one end:of a railway freight car underframe including a center sill 10 with abody bloster 11 connected thereto, both being of welded mild steelconstruction. Each end of the center sill is formed with a striker face12, only one of which is shown. The bolster in this instance comprises apair of diaphragms, of which only one appears in the drawings, eachformed by a pair of vertical web plates 15 in alignment with each otheron opposite sides of the center sill and having their inner ends spacedslightly therefrom, the outer ends extending to the sides of theunderframe. Top and bottom cover plates 16 and 17, respectively, extendover and under the web plates 15, and the upper and lower edges of theplates 15 are secured to the top and bottom plates each by a fillet Weld14 extending along both faces of the web plate and around the inner endthereof, the weld toe, or portion of the weld at the inner plate end,being spaced somewhat from the center sill 10. The center sill issubject at both striker faces to heavy impact loads, which occasion bothtensile and compressive stresses in the bolster. A point of highconcentration of stress is known to exist unavoidably at each weld toe,and under certain applied load and temperature conditions, brittlefracture of a cover plate readily occurs, beginning at such a point andinstantly spreading across the entire cover plate, causing failure ofthe bolster. This invention is directed to preventing brittle fracturebeginning at this point or at a similar point in any comparable weldedsteel structure. In the case of the bolster 11, this is accomplished byproviding in each of the top and bottom cover plates a circular opening22 closely adjacent each weld toe, in alignment with the web plate andof a diameter such as to extend slightly outwardly of the fillet weldson each side of the web plate, or in other words so that the holeextends transversely of the plane of the web plate beyond the edge ofthe fillet weld on each side of the plate. This is best shown in Fig. 2.Upon application of tensile stresses longitudinally of the cover plateloading the material beyond its yield point, deformation will occur atthe portion of the cover plate inwardly of the weld toe without suchstressing of the structure adjacent the weld toe as to initiate brittlefracture, even at low temperatures. The provision of the opening 22 thussuccessfully avoids failure of the bolster due to brittle fracture atthis critical point.

Although superior material and fabrication procedures may improve theperformance :of welded steel structures with respect to brittlefracture, steels of the necessary toughness and ductility are expensive,and special welding techniques and materials are slow and costly, sothat in the case of large structures requiring considerable quantitiesof material, as in railway car construction, the use of such steels andprocedures is ordinarily prohibited by economic considerations. On theother hand, the practice of the present invention permits the use ofrelatively cheap steel and requires no substantial increase in materialor labor costs, while effectively eliminating failures occasioned bybrittle fracture.

Tests were made on full-size specimens of the bolster and center sillconnection portion of car underframes by using a BaldWin-Southwark300,000-lb. tensile testing machine, at F. to simulate low wintertemperatures at which brittle fracture is most likely to occur. Thetests were made by applying tension longitudinally of the cover plateportion of the specimens. Referring par ticularly to Figs. 3 through 5,there is shown a schematic representation of welded structure similar tothe specimens, comprising a flat plate 18 comparable to the web plate 15joined to another flat,- somewhat thicker, plate 19 comparable to thetop cover plate 16. A fillet weld 20 extending on both sides of theplate 18 secures it to the plate 19 in perpendicular relation, the weld20 corresponding to the weld 14 and having a weld toe 21 like that ofthe weld 14. The center sill portion is not indicated, since it had nosignificant effect on the results of the tests. Welded structures otherthan bolsters are of course included in the schematic representations ofFigs. 3 to 5. Tests on the specimens represented by the structure ofFig. 3 resulted in final brittle fracture of the cover plate portion,originating at the weld toe, and extending across the cover plateportion as shown at A, after a total elongation of only a small fractionof an inch and Well before full load was reached, and with little work.Specimens identical to those which had so failed, except for theprovision of a round, smooth-surfaced opening 22 extending through theplate 19 closely adjacent the weld toe 21 and in line with the plate 18,as shown in Fig. 4, were then tested in exactly the same manner. It wasfound that the structure represented in Fig. 4 underwent extensiveelongation, some ten time that of the structure of Fig. 3', and withcorrespondingly increased work, under considerably greater load, withoutfracture. The structure finally failed when the applied load exceededthe ultimate strength of the material, as distinguished from the yieldstrength. The elongation and necking down of the plate 19 :of thestructure of Fig. 4 after the yield point was reached is shown in Fig.5, indicating the plastic deformation possible by reason of provision ofthe opening 22, as against the lack of plasticity or ductility of thestructure of Fig. 3 without the opening. The elongation of the specimenswas taken as an index of theductility or plasticity, or in other wordsthe work required to cause failure. Obviously, structures with theplasticity-providing opening give tremendously improved results in thisrespect. The tests of the bolster and center sill structure specimenswere proved valid by subsequent tests of an entire car incorporating theinvention in the bolster construction as shown in Figs. 1 and 2. The cartests demonstrated conclusively that under conditions which normallywould have resulted in brittle fracture of the cover plate adjacent theinner end of the web plate, there was plastic deformation of the coverplate which prevented failure of the bolster while retaining itsserviceability.

It is not necessary that the opening be round or cir cular, for it maybe elliptical, or elongated with round ends and parallel sides, orotherwise of rounded formation; in short, it must not have any sharpangles or corners, since such might themselves tend to initiate cracks.The surface defining the opening must be smooth, and the edges formedthereby at the opposite faces of the plate likewise must be free ofirregularities. Surface lines in the hole which follow the outlinethereof, that is, which may be considered as lying substantially inplanes parallel to the plane of the plate, are not harmful, but edge orsurface cracks, grooves, or notches in the other direction, that is,more or less perpendicular to the plane of the plate through which theopening is made, must be avoided completely. For these reasons, it ispractically a necessity to drill or machine the opening 22, taking carethat no vertical cracks or notches, even very fine ones, are formed andno crystalline disruption occurs. Accordingly, the hole should not beformed by punching. The opening may be formed in any desired manner,however, if a clean, smooth-surfaced hole is provided and no deleteriouseffect on the surrounding metal results, so that incipient notches orother conditions which might tend to initiate fracture are avoided. Around opening is generally preferred because of the relative ease withwhich it can be provided in a manner meeting the requirements, and alsobecause the circular shape is best suited to avoid fracture undertensile stresses which might be applied in directions other thanlongitudinally of the structure, that is, in directions not parallel tothe weld. An elongated opening provides for greater plastic flow whenthe structure is subject to tensile stresses only parallel to the weld.The opening should have, transversely of the center line of theconnection between the platesor other members, a dimension or width greaterthan the total width of the connection or bond, and be located inalignment therewith. Thus, as in the cases of the structures of Figs. 1to inclusive, in which one plate is secured in abutting relation toanother plate by fillet welds along each side, the opening should bewider than the distance across the two welds, and should besubstantially bisected by the plane of the one plate. Ordinarily, sinceusually there is a standard relation between the size of fillet weldsand the thickness of the members which they secure, the width of theopening is of the order of three or four times the thickness of theplate or other member with which it is aligned. If the abutting plate ormember is secured by a fillet weld along only one face, the opening islocated in line with the fillet weld instead of the plate, and its widthis made somewhat greater than the width of the weld. Again, if the oneplate or member is welded, as by some form of resistance welding, onlyat its abutting edge to the face of another plate or the like, theopening is aligned with the plane of the one plate and has a widthslightly greater than the thickness of the one plate. In other words, asalready stated, the opening is wider than the bond or connection of theone plate or member to the one which it abuts, and is disposed inalignment with the connection. If the opening is elongated, it mustordinarily be arranged lengthwise relative to the welded connection,that is, parallel to the direction of the tensile stresses. Although theopenings are illustrated as extending through the plate adjacent theends of the weld connections, the invention contemplates also theprovision of openings or holes extending only partially through theplate, but of sutficient depth to provide the desired plasticity. Thus,a hole or depression might be formed in the face of the plate on whichthe weld is made, with its bottom merging smoothly with the sides, ortwo such holes might be provided, one in each face of the plate, inopposed relation.

No fully provable explanation of the greatly improved structuralstrength and energy-absorbing capacity or ductility of welded structureshaving the rounded opening provided therein as described has been found.The reason for the results is almost as conjectural as the presentconcepts' of brittle fracture itself. It may be that the stresses tendto approach a state of equi-triaxiality at the weld toe as soon asyielding begins, thus substantially preventing plastic flow and causingbrittle fracture, and that the provision of the roundedv opening resultsin the critical point being out of the region of plastic flow. Anotherpossible explanation may be the material is stressed substantially tothe yield point by the residual tensile stresses due to welding, so thatadded tensile stress due to applied load is very apt to result inbrittle fracture because the material cannot exhibit plastic flow, therounded opening permitting plastic deformation so that redistribution ofstresses may occur, the critical point then being out of the region ofplastic flow. In any case, the question of why brittle fracture occursmost often at low temperatures remains an open one.

The invention is applicable to many other welded steel structures thanthose of the type illustrated in Figs. 3 to 5 inclusive to preventbrittle fracture, some examples of such other structures being shown inFigs. 6,to 9 inclusrve.

In Fig. 6, there is disclosed the steel deck 23 of a ship provided witha hatch one corner of which is shown, formed by a pair of verticalplates disposed at right angles to each other and joined at theircontacting ends by a fillet weld, and also welded to the deck by filletwelds along their outer faces which connect or merge at the corner.Rounded openings 25 are formed in the deck 23, each in line with one ofthe fillet welds 26 securing the plates 24 to the deck, and close to theend thereof, or

inother words to the junction of the welds. Tensile stresses in thedirections indicated by the arrows in Fig. 6, that-is, generally along.or parallel to either of. the hatchdefiningplates 24, willnot result inbrittle fracture, since the openings 25 provide for local plasticdeformation of the deck and allow the material to yield rather thanbreak, without any appreciable impairment of the service ability of thedeck. Thus a potentially very dangerous situation is made safe. A clevismember 27 is also shown in Fig. 6, extending upwardly from the deck 23and secured thereto by a fillet weld 28 about its lower end. Again, byforming rounded openings 25 in the deck in line with the plane of theclevis 27, brittle fracture at either end or toe of the weld 28 isprevented. The openings 25 provided adjacent the clevis are larger thanthose adjacent the hatch corner, since the clevis is shown as formed ofthicker material than the hatch-forming plates 24 and has fillet weldsalong both sides. The openings 25 may be closed by rivets 25a andelastic gaskets 25b, as shown in the figure, so as to be'water-tighteven if they become elongated or otherwise distorted by plastic flow orthe deck 23.

Fig. 7 discloses an I-beam 29 having a clevis 30 secured on the bottomface of the lower flange 31, substantially in the plane. of the web 34of the beam, by aseparate fillet weld 32 on each side thereof, noextension of the welds about the end faces of the clevis being shown inthis, instance. A rounded opening 33 is formed in the lower beam flange31 adjacent each end faceof the clevis, that is, adjacent the weldterminations, in line with the plane of the clevis and the direction oftensile stresses in the beam, each opening extending sufficiently intothe beam web 34 to form an aperture completely through the flange andavoid the possibility of the web affecting the efficacy of the opening.The provision of the openings 33 provides for plastic deformation andprevents brittle fracture at either end of the welds.

In Figs. 8 and 9, a cylindrical pressure tank 35 is shown with an anglebracket 36 for the support thereof welded to the cylindrical or bodywall 37. The edge of the bracket extends parallel to the axis of thetank and is secured to the wall 37 by a single fillet weld 38, whichthus of course extends in the direction of longitudinal tensile stressesin the wall. A rounded opening 39 is formed through the wall 37 closelyadjacent each end of the weld and in alignment therewith, preventingbrittle fracture of the wall at either end of the weld. Hoop stresses inthe Wall do not materially affect the connection of the tank and bracketso far as brittle fracture is concerned. An arcuate-edged' bracketdisposed transversely of the tank and welded to the body wall 37might beused instead of the bracket illustrated, in which case the openings 39would be located closely adjacent the ends of the bracket and theconnecting weld to avoid brittle fracture due to hoop stresses. In suchcase, also, the weld might be a fillet weld extending along both facesof the bracket, and the openings then would be located in line with theplane of the bracket portion engaging the tank. Any suitable means, suchas the bolt, nut, and elastic gasket device 40 illustrated in Fig. 9,may be used for tightly sealing the openings 39.

It will be clear that a pair of plates or like members of differentwidths may be lapped and joined by a single fillet weld along the edgeof the narrower of such members, and openings provided in the widermember at the ends of and in alignment with the weld, substantially asin the case of the tank and bracket construction shown in Fig. 8, forthe prevention of brittle fracture.

It should also be clear that the invention is effective whether thetensile stress of magnitude otherwise sufficient to cause brittlefracture is a predominant stress acting in the direction of the weldconnection or is a com, ponent in that direction of a predominant stressacting at an angle to the line of the weld connection.

While the invention has so far been described only with respect to thestructural aspect, it also provides a method for preventing brittlefracture in welded structures by the imparting to rigid and plastical'lyunyieldingportions,

of such structures a capacity for plastic flow or deformation. Themethod providing by the invention is apparent from the description ofthe structural means employed for achieving the desired plasticity anddoes not require a separate extended explanation. In its broader aspect,the method of the invention comprises the localized removal of materialadjacent a point of high stress concentration where plastic deformationcannot otherwise occur, to provide capacity for plastic flow underconditions which in the absence of such provision would cause brittlefracturej Such localized capacity for plastic deformation is provided bythe method specifically through the employment of holes or openings inthe material adjacent the ends of weld connections between the parts ofthe structure, as hereinbefore explained.

A rather general statement of the application of the invention toprevent brittle fracture is that whenever in a mild steel weldedstructure there is a condition of a high concentration of either or bothapplied and residual tensile stresses and the material adjacent thepoint of such concentration is not relatively free for plastic how so asto neck or thin down or otherwise deform without fracture, the provisionof a rounded hole in the restricted material will provide plasticity toprevent brittle fracture.

What is claimed:

1. A mild steel welded structure comprising a first plate subject totensile stresses, a second plate engaging said first plate extendinggenerally parallel to the direction of said tensile stresses, a weldconnection securing said plates together and terminating on said firstplate at an end of said second plate, and a round smooth-surfacedopening through said first plate located closely adjacent saidtermination of said weld connection substantially in alignment with thecenter line of bond provided by the weld connection and having adiameter slightly greater than the lateral extent of said weldconnection, whereby under tensile stress the first plate will undergoplastic deformation instead of brittle fracture immediately adjacent andbeyond the termination of the weld.

2. A mild steel welded structure comprising a first member subject totensile stresses,.a second member engaging said first member along aline extending generally parallel to the direction of said tensilestresses, a weld connection along said line securing said memberstogether and terminating on said first member at an end of said secondmember, and a round smooth-surfaced opening through said first memberlocated closely adjacent said termination of said weld connection and inalignment with the center line of bond provided by the weld connectionand having a diameter greater than the lateral extent of the weldconnection, whereby under tensile stress the first member will undergoplastic deformation instead of brittle fracture immediately adjacent andbeyond the termination of the weld.

. 3. A mild steel welded structure comprising a first plate subject totensile stresses, a second plate engaging said first plate extendinggenerally parallel to the direction of said tensile stresses, a weldconnection securing said plates together and terminating on said firstplate at an end of said second plate, and a rounded smooth-surfacedopening through said first plate located closely adjacent saidtermination of said weld connection substantially in alignment with thecenter line of bond provided by the weld connection and having adimension transverse of said center line greater than the lateral extentof the weld connection, whereby under tensile stress the first platewill undergo plastic deformation instead of brittle fracture immediatelyadjacent and beyond the termination of the weld.

4. A mild steel welded structure comprising a first member subject totensile stresses, a second member engaging said first member along aline extending generally parallel to the direction of said tensilestresses, a weld connection along said line securing said memberstogether and terminating on said first member at an end of said secondmember, and a rounded smooth-surfaced opening through said first memberlocated closely adjacent said termination of the weld connectionsubstantially in alignment with the center line of bond provided by theweld connection and having a dimension transverse of said center linegreater than the lateral extent of the weld connection, whereby undertensile stress the first member will undergo plastic deformation insteadof brittle fracture immediately adjacent and beyond the termination ofthe weld.

5. A mild steel welded structure comprising a first plate subject totensile stresses, a second plate engaging a surface of said first plateextending generally parallel to the direction of said tensile stresses,a weld connection securing said plates together and terminating on saidfirst plate at an end of said second plate, and a roundedsmooth-surfaced hole formed in the first plate extending from saidsurface located closely adjacent said term-in ation of said weldconnection substantially in alignment with the center line of bondprovided by the weld connection and having a dimension transverse ofsaid center line slightly greater than the lateral extent of the weldconnection, whereby under tensile stress the first plate will undergoplastic deformation instead of brittle fracture immediately adjacent'andbeyond the termination of the weld.

6. A mild steel welded structure comprising a first member subject totensile stresses, a second member engaging a surface of said firstmember along a line extending generally parallel to the direction ofsaid tensile stresses, a weld connection along said line securing saidmembers together and terminating on said first member at an end of saidsecond member, and a rounded smoothsurfaced hole formed in the firstmember extending from said surface located closely adjacent saidtermination of said weld connection substantially in alignment with thecenter line of bond provided by the weld connection and having adimension transverse of said center line slightly greater than thelateral extent of the weld connection, whereby under tensile stress thefirst member will undergo plastic deformation instead of brittlefracture immediately adjacent and beyond the termination of the weld.

7. In a mild steel welded structure including a first plate-like membersubject totensile stresses, a second plate-like member engaging asurface of said first member extending generally parallel to thedirection of said tensile stresses, and a weld connection securing saidmembers together and terminating on said first member at an end of saidsecond member, the improvement comprising a rounded smooth-surfaced holeextending through the first member closely adjacent said termination ofthe weld connection substantially in alignment with the center line ofbond provided by the weld connection and having a dimension transverseof said center line greater than the lateral extent of the weldconnection, whereby under tensile stress the first member will undergoplastic deformation instead of brittle fracture immediately adjacent andbeyond the termination of the weld.

8. In a mild steel welded structure including a first member subject totensile stresses, a second member engaging a surface of said firstmember along a lineextending generally parallel to the direction of saidtensile stresses, and a weld connection along said line securing saidmembers together and terminating on said first member atan end of saidsecond member, the improvement comprising a rounded smooth-surfaced holein said first member extending from said surface located closelyadjacent said termination of the weld connection substantially inalignment with the center line of bond provided by the weld connectionand having a dimension transverse of said center line slightly greaterthan the lateral extent of the weld connection, whereby under tensilestress the first memberwill undergo plastic deformation instead of .9brittle fracture immediately adjacent and beyond the termination of theweld. I r

9. A mild steel welded structure comprising a first substantially flatplatesubject to tensile stresses, at second substantially flat plateengaging a surface of said first plate disposed substantiallyperpendicular thereto and extending generally parallel to the directionof said tensile stresses, a weld connection securing saidplates-together and terminating on said first plate atan end of thesecond plate, and a round smooth-surfaced hole extending through saidfirst plate located closely adjacent said termination of the weldconnection substantially in alignment with the center line of bondprovided by the weld connection and having a diameter slightly greaterthan the lateral extent of the weld connection, whereby under tensilestress the first plate will undergo plastic deformation instead ofbrittle fracture immediately adjacent and beyond the termination of theWeld.

10. A mild steel welded structure comprising a first member subject totensile stresses and having a substantially flat surface, a secondmember having a substantially flat surface and disposed in engagementwith said surface of the first member along a line substantiallyparallel to the direction of said tensile stresses with said surfacessubstantially perpendicular, a weld connection along said line securingsaid members together and terminating on said surface of said firstmember at an end of the second member, and a round smooth-surfaced holeextending through said first member located closely adjacent saidtermination of the weld connection substantially in alignment with thecenter line of bond provided by the weld connection and having adiameter slightly greater than the lateral extent of the weldconnection, whereby under tensile stress the first member will undergoplastic deformation instead of brittle fracture immediately adjacent andbeyond the termination of the weld.

11. A mild steel welded structure comprising a first substantially flatplate-like member subject to tensile stresses, a second substantiallyflat plate-like member disposed substantially perpendicular to saidfirst member engaging a surface of said first member and extendinggenerally parallel to the direction of said tensile stresses, a weldconnection securing said members together and terminating on said firstmember at an end of the second member, and a rounded smooth-surfacedhole extending through the first member located closely adjacent saidtermination of the weld connection substantially in alignment with thecenter line of bond provided by the Weld connection and having adimension transverse of said center line slightly greater than thelateral extent of the weld connection, whereby under tensile stress thefirst member will undergo plastic deformation instead of brittlefracture immediately adjacent and beyond the termination of the weld.

12. A mild steel welded structure comprising a first substantially flatplate-like member subject to tensile stresses, a second substantiallyflat plate-like member disposed substantially perpendicular to saidfirst member engaging a surface of the first member and extendinggenerally parallel to the direction of said tensile stresses, a Weldconnection securing said members together and terminating on said firstmember at an end of the second member, and a rounded smooth-surfacedhole formed in the first member extending from said surface locatedclosely adjacent said termination of the weld connection substantiallyin alignment with the center line of bond provided by the weldconnection and having a dimension transverse of said center line greaterthan the lateral extent of the weld connection, whereby under tensilestress the first member will undergo plastic deformation instead ofbrittle fracture immediately adjacent and beyond the termination of theWeld.

13. A mild steel welded structure comprising a first substantially flatplate subject to tensile stresses acting in different directions, a pairof plates engaging said first plate arranged at an angle to each otherwith adjacent ends in engagement and each' extending generally parallelto one of said tensile stress directions and substantially perpendicularto said first plate, a weldconnection securing each of said pair ofplates to said first plate and terminating on said first plate at saidends of the pair of plates, and a pairof rounded holes extending throughsaid first plate each located closely adjacent the termination of theweld connection between one of said pair of plates and said first plateand in alignment with the center line of bond provided by that weldconnection and each having a dimension transverse of the respective weldconnection slightly greater than the lateral extentof said weldconnection, whereby under tensile stress the first plate will undergoplastic deformation instead ofbrittle fracture immediately adjacent andbeyond the termination of the Weld.

14. A mild steel welded structure comprising a substantially flat platesubject to tensile stresses, a generally plate-like member disposedsubstantially perpendicular to said plate in engagement with a surfacethereof and extending generally parallel to the direction of saidtensile stresses, a weld connection securing said member to said plateand terminating on said plate at opposite ends of said member, and apair of rounded smooth-surfaced holes extending through the plate eachlocated closely adjacent one termination of the weld connection substantially in alignment with the center line of bond provided by the weldconnection and having a dimension transverse of said center lineslightly greater than the lateral extent of the Weld connection, wherebyunder tensile stress the plate will undergo plastic deformation insteadof brittle fracture immediately adjacent and beyond the termination ofthe weld.

15. A mild steel welded structure comprising an I-bearn subject tolongitudinal tensile stresses, an apertured platelike clevissubstantially perpendicular to a flange of the I-beam extendinggenerally parallel to the direction of said tensile stresses andsubstantially centered relative to the plane of the web of the I-beam, aweld connection securing the clevis to said flange terminating on theflange at opposite ends of the clevis, and a pair of roundedsmooth-surfaced holes extending through said flange and into said webeach located closely adjacent one termination of the Weld connectionsubstantially in alignment with the center line of bond provided by theweld connection and having a dimension transverse of said center lineslightly greater than the lateral extent of the weld connection, wherebyunder tensile stress the flange will undergo plastic deformation insteadof brittle fracture immediately adjacent and beyond the termination ofthe weld.

16. A mild steel welded structure comprising a flanged member subject totensile stresses, a generally plate-like member disposed substantiallyperpendicular to a flange of said flanged member in engagement with asurface thereof and extending generally parallel to the direction ofsaid tensile stresses, at weld connection securing said plate-likemember to said flange and terminating on said flange at opposite ends ofsaid plate-like member, and a pair of rounded smooth-surfaced holesextending through the flange each located closely adjacent onetermination of the weld connection in alignment with the center line ofbond provided by the weld connection and having a dimension transverseof said center line slightly greater than the lateral extent of the weldconnection, whereby under tensile stress the flange will undergo plasticdeformation instead of brittle fracture immediately adjacent and beyondthe termination of the weld.

17. A mild steel welded structure comprising a curved plate subject totensile stresses, a substantially flat plate engaging said curved plateextending generally parallel to the direction of said tensile stresses,a weld connection securing the plates together and terminating on saidcurved plate at an end of said fiat plate, and a rounded 11 gsmooth-surfaced opening extending through said curved plate locatedclosely adjacent said termination of the weld connection substantiallyin alignment with the center line of bond provided by the weldconnection and having a dimension transverse of said center lineslightly greater than the lateral extent of the weld connection, wherebyunder tensile stress the curved plate will undergo plastic deformationinstead of brittle fracture immediately adjacent and beyond thetermination of the weld.

18. A mild steel welded structure comprising a curved member subject totensile stresses, a member engaging said curved member having asubstantially fiat surface extending generally parallel to the directionof said tensile stresses, a weld connection securing the memberstogether and terminating on said curved member at an end of saidflat-surfaced member, and a rounded smooth-surfaced hole formed in saidcurved member extending from the surface thereof engaged by saidfiat-surfaced member located closely adjacent said termination of theweld connection and in alignment with the center line of bond providedby the weld connection and having a dimension transverse of said centerline slightly greater than the lateral extent of the weld connection,whereby under tensile stress the curved member will undergo plasticdeformation instead of brittle fracture immediately adjacent and beyondthe termination of the weld.

References Cited in the file of this patent *UNITED STATES PATENTS2,382,584 Scheyer Aug. 14, 1945 FOREIGN PATENTS 102,367 Australia Oct.27, 1937

